High efficiency filter aid

ABSTRACT

Simultaneously improved flow rate and turbidity removal by adding to the turbid solution to be filtered an animal protein gelatin or glue, or by coating a filter aid with an animal protein gelatin or glue.

United States Patent Davis et al.

[ 51 Apr. 25, 1972 [54] HIGH EFFICIENCY FILTER AID [72] Inventors:Donald William Davis, Clinton; James Michael Baloga; Bruce ChamberlinOlmstead, Jr., both of Somerville, all of NJ.

Johns-Manville Corporation, New York, NY.

[22] Filed: Dec. 18, 1970 [21] Appl.No.: 99,376

[73] Assignee:

Related U.S. Application Data [62] Division of Ser. No. 458,883, May 26,1965, Pat. No.

U.S. Cl ..210/504 Field of Search ..210/36, 52-54, 210/75, 500-506;252/181, 428

[56] References Cited UNITED STATES PATENTS 706,075 8/1902 Subberger..210/54 X 2,937,143 5/1960 Goren ..210/52 3,165,465 1/1965 Ray et al.3210/54 X 3,235,492 2/1966 Andersen et al. 210/36 X 3,247,106 4/1966Sopoci..... .....2l0/52 3,252,898 5/1966 Davis 210/75 X 3,335,869 8/1967Hedges .1 ...210/500 3,562,154 2/1971 Davis et al. ..210/36 PrimaryExaminer-Reuben Friedman Assistant Examiner-R. W. Burks Attorney-John A.McKinney and Robert M. Krone 5 7] ABSTRACT Simultaneously improved flowrate and turbidity removal by adding to the turbid solution to befiltered an animal protein gelatin or glue, or by coating a filter aidwith an animal protein gelatin or glue.

7 Claims, 5 Drawing Figures CEu TE N0 545 (EL/TE No. 5

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HOURS ELAPSE D TIM Patented April 25, 1972 3,658,184

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9.1. a ugm Arroewsv HIGH EFFICIENCY FILTER AID This is a division ofapplication Ser. No. 458,883, filed May 26, 1965, now U.S. Pat. No.3,562,154.

This invention relates to an improved method of removing finely dividedinsoluble materials from liquids. It is especially concerned with theremoval of suspended colloidal matter from water-based liquids, such asthe clarification of beer and the removal of turbidity from water. Morespecifically, this invention relates to filter aid filtration whichconverts insoluble materials to a filterable state by attachment to arigid filter aid particle.

Of the many impurities found in water-based liquids, turbidity is amongthe most troublesome. Turbidity is defined as a lack of clearness in theliquid, but should not be confused with color, for a liquid may be darkin color, but nevertheless clear and not turbid. This lack of clearnessis primarily due to suspended matter in a finely divided state and maybe the result of silt, organic matter, microscopic organisms, andsimilar materials. Consequently, turbidity is the measure of the opticalobstruction of light passing through the liquid, caused by the suspendedparticles rather than in any terms of weight concentration.

The removal of finely divided solids and colloids from water-basedliquids has been attempted for many years. Filtration has been used foreffecting this removal by forcing the liquid, under a pressuredifferential, through a filter medium, with slow sand filters being thefirst structures devised to accomplish this. These sand filters have hadseveral disadvantages including the inability to handle effectively manytypes of contamination found in water supplies and such low capacitythat large areas and expensive construction have been required. Coarsersand structures, termed rapid sand filters, which act largely asstraining devices have been subsequently employed.

It is important to understand that these filters themselves have littleinherent clarifying capacity in that the suspended matter mustnecessarily be treated to collect or coalesce into sufficiently largeagglomerates so as to settle out and be substantially removed in advanceof the rapid sand filters.

The processes which cause this coalescence have been termed pretreatmentamong water-works engineers and operators. Almost never is thenon-pretreated water filtered through a rapid sand filter if highquality filtered liquid is desired, and it is commonly understood thatthe term sand filter plant" includes the pretreatment works which aresubstantially larger and more expensive than the sand filter structuresthemselves. This technique is more fully explained in Betzs Handbook oflndustrial Water Conditioning.

ln this treatment a coagulant is added to the liquid as the agentnecessary to facilitate the settling out of the colloidal or finelydivided suspended matter. The coagulants themselves are made effectivesuch as by agitation and flocculation. U.S. Letters Patent Nos.2,393,269; 2,937,143; and 3,066,095 are representative of the prior artteachings utilizing this technique of first settling and then filtering.Because the size and cost of the foregoing processes make themunavilable to most processors, small communities and industries havecontinued to have difficulty associated with the treatment ofwater-based liquids.

Recently innovations have been put forth purporting to improve rapidsand filter turbidity removal performance when, in reality they areimprovements to the pretreatment process which precedes the actualfilter operation. The reason for this becomes apparent, when it isunderstood that any appreciable amount of residue not removed bysettling from the filter infiuent will quickly tend to clog the filterand produce impractical head losses in relatively short and uneconomicaltime span.

While the above might be termed the traditional approach to liquidfiltration, the principle of filter aid filtration has been advanced toeffect clarification of water-based liquids. Certain economics resultfrom the simplicity of the process as the requirements for large andexpensive structures to provide for floc formation or particleattachment and settling periods are reduced or eliminated.

This technique involves the incorporation of a small amount of finelydivided particulate filter aid material in the liquid to be filtered. Byso doing, the filter aid functions to form continuously a porous cakeupon the filtering medium surface and in actuality, to entrap impuritiesby various mechanisms. The materials most generally used as filter aidsare diatomaceous silica, perlite, and other siliceous materials, carbon,and fibrous matter, such as asbestos and cellulose, and mixtures ofthese. A particularly important feature of the filter aid filtration isthat the pores of the surface of the filter aid cake are far smallerthan those in the filter septum, thereby enabling the removal of a verysubstantial portion of the suspended particles. The proportion removedwill, of course, be a function of the size and the nature of theparticles to be filtered and the porosity and inherent clarifyingability of the particular filter aid. This technique, therefore, is tobe distinguished from the pretreatment bed filtration as all the liquidswith the suspended solids is passed to the filter per se.

It was early determined that the technique could be improved by treatingthe filter aids so as to cause the impurities to affix themselves to thefilter aid particles and thus filter out along with the filter aid. Thean observed that many colloidal impurities in aqueous liquids areelectro-negative and, therefore, proposed that an electro-positivefilter aid be used so as to attract the impurities by this mutualelectrical attraction.

One of the earliest disclosures of such a technique is that described inU.S. Letters Patent No. 2,036,258. The patentee therein proposes toflocculate upon the surface of the filter aid a hydrate of a multivalentinorganic salt which may be converted to the hydroxide by proper pHconditions of the liquid being used. Various other techniques have beenadvanced as improvements upon this technique and these may beillustrated by the disclosures in U.S. Letters Patent No. 3,235,492patented on Feb. 15, 1966 and No. 3,247,106 patented on Apr. 19, 1966,and assigned to the instant assignee.

Even with these advances, some difficulty remains in completely andeffectively removing finely divided turbidity and other colloidal matterfrom water-based liquids and accordingly, the art has continued to seekadditional techniques to achieve effective removal.

One of the principal concerns of the art is to provide filter aids withhigher clarifying capacity while maintaining high flow ratecharacteristics which dictates the filtration efficiency. Another areaof interest to the filtration art is to provide a filter aid which willeffectively reduce turbidity and the like to acceptable levelsregardless of variations in the amount of turbidity of the liquid as itpasses through the filtration cycle.

It is accordingly a principal object of this invention to provide a morepractical and effective means whereby the deficiencies of the foregoingfilter aid filtration processes are overcome.

It is a further object of this invention to provide a method ofclarifying and substantially purifying water-based liquids by filter aidfiltration whereby maximum effectiveness and improved filtrationcharacteristics are achieved as to removal of turbidity, color and otherinsoluble suspended particles.

lt is another object of this invention to provide a new and morepractical method of treating water-based liquids by providing improvedflow rate filter aid materials without any deleterious effects as to theclarification and purification of the water.

It is another object of this invention to provide a practical means ofpurifying turbidity contaminated water sources to render them potable.

Additional objects and further scope of applicability of the presentinvention will become apparent in the detailed description givenhereinafter.

It has now been determined that the foregoing objects may be satisfiedand the above-mentioned problems lessened by providing a novel method oftreating the insoluble contaminant laden water-based liquids. It hasbeen discovered that the technique of filter aid filtration may beimproved by using a protein colloid in conjunction with conventionalfilter aid based materials. More specifically, it has been determinedthat certain protein colloids, i.e., gelatin and glue, having specificgel strength, may be combined either as a coating upon or as a physicalmixture with the filter aid in the liquid to be treated, and preferablyused under proper pH conditions to maintain the protein colloid belowits isolectric point, generally about a pH of 8, to remove efficientlyand effectively insoluble impurities contained in the water by standardfilter aid filtration techniques.

The chemistry of gelatins and glue is a much discussed and reviewedportion of chemistry. It is generally recognized, however, that gelatinis an organic nitrogenous colloidal substance of the protein class whichis derived by the selective hydrolysis of collagen from the skin,connective tissue and bones of animals. Glue, on the other hand, is animpure or degraded form of gelatin obtained by reaction of heat andwater on the same base material. Generally the gelatin is selected andtreated with a special care so that the resulting product is cleaner,purer, and generally clearer in color than glue. Much has been writtenon the chemistry of these protein colloids and, perhaps, one of the bestdisclosures of that chemistry is that entitled Gelatin, the CurrentPosition" by A. G. Ward, Journal of the Society of Leather TradeChemists, Vol. 44, 1960, Pages 505-518.

While recognizing gelatin and other protenaceous materials have beenused in the treatment of wine in combination with settling techniques toremove soluble materials (such as represented by U. S. Letters PatentNo. 706,075 and others cited above), the art has failed to appreciatethat gelatin, when controlled under proper pH conditions and incombination with filter aid filtration, may be used to extremelysurprising advantages in the removal of suspended insolubleparticulatematerial from water-based liquids. It has been determined that thecombination of small quantities of gelatin with the body feed in astandard filter aid filtration technique has produced many advantages.This is effected either as a coating upon the filter aid or as aseparate addition to provide a mixture within the liquid to be treated.

Specific advantages have involved improved head loss rates to clarityratio as contrasted with the filter aid per se, im proved clarity at theinitial portion of the filtration cycle, improved ability to handle ahigh influent turbidity while maintaining consistent and constanteffluent turbidity, and improved ability to hold low effluent turbiditydespite influent fluctuations without immediate filter blockage andshortened filtration cycles.

FIG. 1 discloses the relative rates of flow obtained with f- CELITE"Filter Aids in an average industrial clarification.

FIG. 2 compares a CELITE 503 Filter Aid versus a CELITE 503 Filter Aidin combination with added SWIFTS 7 l Gelatin.

FIGS. 3a and 3b compare CELITE 512 to the combination ofCELITE 503 plusthe SWIFTS 710.

FIG. 4 illustrates an evaluation of alternative sources and grades ofprotein colloid.

It has been determined that the addition of the protein colloid in anamount between 0.02 and 20.0 parts per million (ppm) based on the liquidto be treated, when added in combination with the filter aid, improvesthe filter liquid clarity. With regard to the treatment of water, 0.2 to2.0 ppm is generally sufficient. As to industrial treatment, the amountof addition is dependent upon the degree of contamination and thedesired purity. The amount of filter aid used, likewise, variesdependent upon the liquid being treated but generally varies between 2and 200 ppm. A more complete understanding of the invention will becomeapparent from the examples herein of the operation within the scope ofthe invention.

Before discussing the specific examples, it is believed desirable toappreciate fully the filtration effects of certain commerciallyavailable filter aids. A class of diatomaceous silica filter aids soldunder the trademark CELITE" have been produced having a variety of Howrate and clarifying capacities. Generally speaking, the higher theclarifying capacity of the filter aid, the lower the flow rate. Therelative flow rates of these filter aids are shown in the graph in theaccompanying drawings identified as FIG. 1.

The following equipment and test procedure were used to evaluate theinstant invention. Two single element test filters were used with directfeed and pressure supplied by a selfpriming centrifugal pump. Slurriedbody feed and other ingredientswere pumped into feed lines against rawwater pressure. A detention tube was used in one of the filter lines togive a 3-minute contact time for body feed or additives ahead of thefilter. The filter medium per se was precoated in a conventional fashionat one-tenth of a pound per sq. ft. of filter area. Turbiditycalculations were made by taking samples from the common raw waterheader and from each filter effluent line. The body feed additions weremade up as a slurry in a SO-gallon tank using the raw water for thecarrier. The slurry was fed at about 150 ml per minute to the rawwaterline ahead of the filters using the diaphragm pump. In some runsthe regular filter aid was slurried up in the tank and thensufficientprotein colloid solution was introduced to obtain the desiredaddition.

When separate additions of protein colloid were desired. a separatelystirred solution tank and diaphragm pump were installed with a separatepumping line to the raw water line. Thus the filter aid was pumped intothe raw water stream separately from the protein colloid solution.

In the accompanying tables, the amount of protein colloids used isstated as mg per g, as well as parts per million. The mg per g is themilligrams of additive used per gram of body feed and is the term bestapplicable to coated filter aid. The term head loss is the averageincrease in the pressure per hour required to maintain 1 gallon persquare foot flow rate. It is stated in pounds per hour with the averagepressure filter having 35 pound pressure rise available for a cycle.Filtration cycles were generally terminated by time without reachingterminal head losses. It is important to note that in this type offiltration and generally in diatomite filtration, the cycle isterminated by pressure increase rather than by breakthrough. Most cycleswere run 5 to 6 hours before termination to make direct comparison ofthe data more valid.

EXAMPLES I Xlll Gelatin (SWIFT 710) additions of between 0.02 and 0.08parts per million were employed in these specific examples, varyingaccording to the above procedure.

The coated examples were made by coating SWIFT 710 gelatin on CELITE 503filter aid at three levels of gelatin addition. The SWIFT 710 gelatin isa food grade gelatin of approximately 300 Bloom gel strength andcoatings were made at the levels of 1.9, 2.9, and 5.8 mg of gelatin pergram of filter aid. A 1 percent solution of gelatin was sprayed into aribbon mixer containing the CELIT E 503 filter aid. The batches weredried below 220 F above which the gelatin would degrade.

The data from .these runs is summarized in Table I below showingsignificant differences in the head loss and effluent turbidity when lowconcentrations of gelatin were used and the effectiveness of the coatedfilter aid versus the separate addition of the filter aid and thegelatin material. Coated precoat filter aid was used in all cases.

TABLE 1 [Swift 710 coated Celite 503 filter aid study by coatingconcentration] Swift 710 B.F./ Average concentration turturbidity Headbidity loss, Run number MgJg. P.p.m. ratio Raw Efi. lb./lu'.

1.9 0.03 1.5/1 11.3 1.4 2.6 2. 9 0. 05 1. 4/1 11.3 1.35 I. 7 5. 8 0.0S 1. 6,-"1 S. .3 1.1 5. 6 2. \l 0, 03 l. '1 ti. 3 1. ti 0. 3G .3 .l 0.03 1. S 'I (i. t) l. 3 0. (H .2. .l 0. 03 1.8/1 ti. 6 l. 2 0. 7T '2 J0.05 .2. 5 /1 6. 4 l. 1 ll. 2*.)

1 All runs using coated filter aid for precoat and body feed. 2Three-minute detention ahead of filtration.

Swift 710 B.F./ Average concentration turturbidity Head Addition bidityloss, Run number method Mg./m. P.p.m. ratio Raw E11. lb./hr.

1 Coated 1. 5 0.03 1. 5/1 11.3 1.4 2. 8... Separate-- 1 45 0.03 1.9/111.8 1.15 1.1 9... Coated 1. 9 0. 07 2. 25/1 16. 3 l. l. 1 10..Separate.--. 1.6 0.06 2.4/1 16.3 1. 5 0. 7 5... Coated 2. 9 0.03 1.8/16. 6 1. 3 0.6 11 Separate 2.0 0. 04 2. 8/1 7. 4 1. 5 0. 7 Coated... 5.80.56 2.2/1 43.1 4.0 0.9 13 Separate.... 5.3 0.48 2.1/1 43.1 1.0 6.8

1 Three-minute detention ahead of filtration. g

The improve clarity achieved by the low concentration 1 5 Example XlVshows this 1mprovement with a low turbidity treatment is representedgraphically in FIG. 2. Each line on the graph represents the averagefiltered water turbidity for a group of runs made under similarconditions. Three groups with raw water turbidity ranges of 5-10, -20,and 30-50 are shown. Similar groups are also shown using body feed ofCELITE S03 filter aid, a high flow rate filter aid, and using CELITE 503filter aid with SWIFT 710 gelatin. The improved average clarity of theruns with the gelatin addition is shown in a comparison of the lines ofequal raw water turbidity. The excellent clarity at the beginning of therun is also illustrated in this figure. All average turbidities for therun with the gelatin addition were below 3 turbidity units after 15minutes of the cycle, while without gelatin addition, the averageturbidity ranged from 3.25 to 16.4, dependent upon the raw waterturbidity. Excellent removal was achieved at low turbidity level.Filtered water with turbidities below the maximum acceptable limit isproduced from raw water when turbidity ranges from 7 to 36 units. Thelines for filtered water when using gelatin for all three turbiditygroups are in the same band showing a constantly good filtered waterturbidity.

EXAMPLES XIV XXVlI Since separate addition of the gelatin and the filteraid appeared to give good turbidity removal result, a series of testswere made against several grades of filter aid. These results aredemonstrated below in Table 2. Previous testing had established thataddition of gelatin improved turbidity removal when added with CELITE503 filter aid.

of raw water. Examples XVI and XVlll were made with a much higherturbidity raw water and established the removal efficiency of theprotein colloid CELlTE 503 filter aid combination, when compared withHYFLO SUPER-CEL filter aid which is considered a more effective filteraid than the CELlTE 503 filter aid as far as clarity is concerned. (SeeFIG. 1) The high dosages of protein colloid effected a reduction ofturbidity from 30 units to less than 1.5 in a short period of time andpermitted an extended cycle for runs which correspond to Examples XXXXVll, with the uneven numbered runs corresponding to use of filter aidper se of a high clarity capacity and demonstrated the ability of thegelau'n and filter aid to maintain the clarity expected from the highclarity filter aid (CELITE 512 filter aid), while maintaining headlosses well below those corresponding to this filter aid. This is alsodemonstrated in FIGS. 3aand 3b. It is again significant to note that theuse of the combination of protein colloid and filter aid produced aconsistency in the average effluent turbidity at 1.1 to 1.4 unitsdespite the varied change in the average raw water turbidity from 7.4 to34.5.

EXAMPLES XXVlll XXXVII Having thus demonstrated the effectiveness of oneprotein colloid, i.e., the SWIFT 710, a complete investigation wasconducted on addition types of protein colloid. The data from these runsare presented in Table 3 below.

As seen from the table, all the gelatin and the CELITE 503 filter aidcombinations tested were effective in obtaining good TABLE 2 [Separateaddition of Swift 710 gelatin and Cclite 503 filter aid vs variousfilter aid grades Swift 710 B.F./ Avg. turbidity llend Body 10mlturbidit loss. ltun number MgJg. l.p.m. 111111 precout rntio Rnw E11.lb./l1r

Colite 503 4.1/1 7.? 1.3 0.2 7 {Cclitc s03 a. 7/1 7. 7 1.8 0.3 5 0 0 47{Celito 503 2. 7/1 3-1. 5 l. 3 3.0 Hyilo super 001.. 2. 7/1 34. 5 6. 6(1. o 6 3 0 Celite 503 1. 0/1 32. 5 1. 2 4. 4 Hyflo super cel 1. !)/132. 5 4. 5 1.1 2 3 0 09 {Celito 503 2. 8/1 14.1 1. 3 0. 75 Cclite 5122.0/1 14.1 1.7 3. 0 1 3 0 03 Celite 503 2.3/1 8.5 1.4 1.0 Celite 512 1.0/1 8. 5 1.0 2. 25 2 0 2. 8/1 7.4 1.2 0.7 3 O/l 7. 4 1. 1 1. 1 2 2 1.0/111.8 1.1 2.8 1.0/1 11.8 1.0 3.6

1 Three minutes detention ahead of filtration. r r T TABLE 3 [Separateaddition 01 various Swift gelatins and Celite 503 vs Celite 503] Avg.Addition B.F.' turbidity Head Run Precoat and turbidity 55. No. GradeMg./g. P.p.n1. body feed ratio Raw Pitt. 11). hr.

28"... Swift- 410 i Cel1te 503 10.0 1.. 1.1 g'gg i {Genre 503 10.0 1.51.3 -I iCelitv s... 1'.5 1s 3.: 31....42? tonne 503". i. s 1 .1 1. :132. wi t 210 j iC0l11t503... 10.0 1.11 1.4 3 2339 M tor-1115503." 11 .111.1 a. 34.. ".1. ((clilo 503 1.8 U. 1 ms"- b\\ 111. 3/11. 3.1 ll. 10Uvmo 503- V L T 1 1(1'li11503. 1. n 1. n 37... i 1mm. 50:1 5. o 1 4 1High nvurugo llltilllSl 01 high unrly reading rnusuddrr Into sinrl ofSwift 10 addition turbidity removal and better than average removal thanCELlTE 503 filter aid with the exception of the one run. Head losseswere good when turbidity removal is considered.

An evaluation was also made of the separate solution of colloid per gramof CELITE 503 filter aid to a standard sugar filtration test. Theresults obtained are illustrated in FIG. 4.

The correlation of clarity with gel strength of both type A and type Bprotein used were developed by regression analysis of the data and aresignificant at the 90-95 percent levels. Little differences betweenequivalent grades of different manufacturers were found. All productstested were food grade products, although technical grade equivalentshave been found to work. Several grades of glue were also tested so asto evaluate completely the protein colloids. Gel strength as low as 60grams Bloom were employed and are equivalent to about 75-100 Bloomstrength type B gelatin. The Bloom strength ranged from about 60 toabout 300 and included both I type A and type B gelatin.

While the invention has demonstrated exceptional value in removinginsoluble contaminants, it is also useful for removing color and similarsoluble impurities.

It is believed that the above provides a complete description of theinvention in such manner as to distinguish it from other be made withoutdeparting from the spirit of the invention. it is also to be understoodthat the scope of the invention is not to be interpreted as limited tothe specific embodiments disclosed herein, but only in accordance withthe appended claims, when read in light of the foregoing description.

What we claim is:

l. A composition of matter particularly adapted for filter aidfiltration consisting essentially of between 0.2 and 20 parts proteincolloid of animal origin and between 2 and 200 parts particulate filteraid.

2. A composition of matter as defined in claim 1 wherein said proteincolloid is coated upon said filter aid.

3. A composition of matter as defined in claim 1 wherein saidcomponents'are in the form of an intimate physical mixture.

4. A composition of matter as defined in claim 1 wherein said proteincolloid has a gel strength of between 60 and 300 gram Bloom.

5. A composition of matter as defined in claim 4 wherein said proteincolloid is gelatin.

6. A composition of matter as defined in claim 4 wherein said proteincolloid is animal glue.

7. A composition of matter as defined in claim 1 wherein said filter aidis selected from the group consisting of diatomaceous silica, perlite,and mixtures thereof.

t I! 1 i i

2. A composition of matter as defined in claim 1 wherein said proteincolloid is coated upon said filter aid.
 3. A composition of matter asdefined in claim 1 wherein said components are in the form of anintimate physical mixture.
 4. A composition of matter as defined inclaim 1 wherein said protein colloid has a gel strength of between 60and 300 gram Bloom.
 5. A composition of matter as defined in claim 4wherein said protein colloid is gelatin.
 6. A composition of matter asdefined in claim 4 wherein said protein colloid is animal glue.
 7. Acomposition of matter as defined in claim 1 wherein said filter aid isselected from the group consisting of diatomaceous silica, perlite, andmixtures thereof.